Battle Creek's Commander Guziewicz (Janet McTeer) turns out to be a heartbreaker when she's not on duty.

When her house burned down in Sunday's episode, a string of 17 exes were hauled down to the station as suspects, each one telling a sadder story of being dumped by the seemingly buttoned-up Guziewicz. As the mystery behind the arson unraveled, so too did the more surprising backstory between Guziewicz and her adopted son, Danny (Rotimi).

When Danny was 3, he was hiding in a closet when his parents were murdered in a drug-related killing. Guziewicz was one of the officers who responded to the scene. She took him home and raised him, until he got caught up in drugs and crime. She threatened not to see him until he was clean, and he responded by cutting her out of his life completely.

That hidden guilt has weighed on Guziewicz for three years, says McTeer.

"He was the kid with the messed-up background, but she was the one who couldn't cope," McTeer tells The Hollywood Reporter. "She feels he let him down, and actually they're not that dissimilar."

To prepare for stepping into the spotlight for this episode, the two-time Oscar nominee spent time getting into the mindset of a person dealing with family trauma and working through the backstory with producer Esta Spalding, who penned the episode.

"Perhaps for somebody like Guziewicz, her way of coping with things is just to walk away," says McTeer.

The episode leaves off with Guziewicz deciding she's not going to give up on her son, even if he doesn't want her around. That storyline will come back several episodes down the road, when Danny returns to ask his mother about his dark history.

"The episode explores what happens when things come back and hit you in the face and you can't walk away," says McTeer.

McTeer's first big episode wasn't all heavy drama. McTeer relished getting to play the heartbreaker aspect of her character, crediting Spalding for crafting the idea of making her seemingly uptight character not so uptight after all.

"The idea was for her not to be a stereotypical boss," says McTeer. "What Esta came up with was quite funny."